Optical communication systems have come into widespread use and various types of optical modules are now in practical use. Examples of modules placed in practical use include modules including an optical modulator, an optical amplifier, an optical transmitter, an optical receiver, or an optical switch.
Commercially available optical modules include often an input optical fiber and an output optical fiber coupled thereto. The input optical fiber is optically coupled to the input end of an optical device such as, for example, an optical modulator, optical amplifier, optical transmitter, optical receiver, or optical switch in an optical module. The output fiber is optically coupled to the output end of the optical device. To reduce the coupling loss of the optical module, therefore, it is desirable to precisely align the ends of the input optical fiber and output optical fiber to the optical device.
When an optical module to which an optical fiber (an input optical fiber, an output optical fiber, or both) is connected is manufactured, the position of the end of the optical fiber is detected with respect to an optical device in the optical module. The position of the optical fiber is detected by, for example, using an electronic camera to photograph the optical fiber. The optical fiber is then aligned according to the detection result so as to reduce the coupling loss of the optical module.
As a related technology, a method is provided in which an optical part such as, for example, a waveguide, and an optical fiber are easily coupled with high precision (see Japanese Laid-open Patent Publication No. 8-146242, for example). In another method provided, the inclination of an end surface of a cylindrical member is highly precisely measured relative to the side surface of the cylindrical member (see Japanese Laid-open Patent Publication No. 2006-214753, for example). In still another method provided, a charge-coupled device (CCD) camera is used to inspect a defect on a thin film (see Japanese Laid-open Patent Publication No. 7-301608, for example).